Implications of Changes in Ambient and Climatic Conditions on Ecosystem Processes

Abstract

Climate has a chemical component that is of considerable importance for ecosystems. The deposition of naturally formed nitrogen Compounds like nitrate and ammonium and of trace elements like those originating from sea spray can be decisive factors in plant growth and ecosystem development. Among natural airborne particulate matter, sea-salt aerosols are chiefly deposited in coastal and sub-oceanic regions (for example, in coastal and central Europe). Major constituents of sea-salt aerosols are Na, Mg, Cl and sulphur (in the form of sulphate, S042-), causing elevated inputs of these elements (Junge and Werby 1958). Ecosystems can also be subjected to the deposition of particulate matter produced in arid and sub-arid regions by wind erosion of soil minerals (Sahara dust), and to the deposition of particulate matter ejected into the atmosphere by volcanic eruptions. Dust particles and aerosols are frequently subjected to mid-range transport and are deposited in the regions downwind of the source, or they may even undergo hemispheric or global long-range transport. Thus, approximately 20% of 1 Pg of soil particles entering the atmosphere from arid regions are subjected to long-range transport (diameter class less than 1 Jim); soil particles from the Sahara form a major component of ocean sediments in the North Atlantic (Schütz 1980; Prospero et al. 1981; Pye 1987). However, man has increasingly perturbed the irradiation features (albedo; Chap. 4; Sect. 7.1) and composition of the atmosphere via the generation of dust and the emission of gases like sulphur dioxide (S02), which has also changed the chemical climate. On a local scale, these changes date back to the Bronze Age; with industrialisation, they reached the continental scale.